High dynamic range &amp; depth of field depth camera

ABSTRACT

In order to maximize the dynamic range and depth of field for a depth camera used in a time of flight system, the light source is modulated at a plurality of different frequencies, a plurality of different peak optical powers, a plurality of integration subperiods, a plurality of lens foci, aperture and zoom settings during each camera frame time. The different sets of settings effectively create subrange volumes of interest within a larger aggregate volume of interest, each having their own frequency, peak optical power, lens aperture, lens zoom and lens focus products consistent with the distance, object reflectivity, object motion, field of view, etc. requirements of various ranging applications.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention claims priority from U.S. patent application Ser.No. 61/594,745 filed Feb. 3, 2012, which is incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to a high dynamic range and depth of fielddepth camera, and in particular to a depth camera, which has a pluralityof frequency, peak optical power and integration period settings withineach frame time for use in a time of flight based camera system.

BACKGROUND OF THE INVENTION

In traditional photography, depth of field (DOF) is how much of yourimage is in focus. Shallow depth of field refers to when only thingsthat are very close to the plane of the subject you focus on are infocus. Objects that are behind or in front of your subject will appearout of focus. Dynamic range refers to the difference between yourhighlights and shadows in an image. On average, the human eye can seedynamic range on the order of 1,000,000:1. What this means is that wecan see details in both very bright and very dark areas of a scene atthe same time. A digital sensor has a dynamic range on the order of1,000:1, which means that if your subject is very bright compared toyour background, when you expose the image correctly for your subject,you background will appear to be very dark. Conversely, if you exposedthe image for the background, your subject may appear “blown out” orvery bright white and overexposed.

As with traditional photography cameras, depth of field, i.e. imagesharpness consistency within the camera Field of View (FOV) and range ofinterest, and image dynamic range, i.e. image contrast range within thecamera FOV and range of interest, requirements can be a significantchallenge to a depth camera. In the case of a depth camera, objectsclose to the camera's light source and or of high reflectivity can causeover saturation of sensor pixels while objects further from the camera'slight source and or of low reflectivity can be difficult for thesensor/camera to detect at all.

A “Time-of-Flight” based depth camera comprises a depth image sensor,which is typically made using a standard CMOS fabrication process, andan IR light source for measuring distance, which is proportional to thelength of time the IR light takes to travel from and return to thecamera. A depth camera system generates depth images and transmits themto the host processor over a suitable, e.g. USB, interface.

The camera hardware includes a light source module, an IR lightdetecting, e.g. CMOS, image sensor, and an ambient light-color sensing,e.g. CMOS, image sensor. A 3D imager produces phase measurements thatare processed either on sensor or in a remote coprocessor to produceactual range data. Such a camera can be used in “Z-only” mode forapplications, which require the use of range data only. The camera couldalso be used in “RGB+Z”, i.e. full 3D depth and 2 dimensional colors,modes for applications which utilize both traditional color as well asdepth images. Depth and color processing can be done in the camera orwith a pass-through mode in which unprocessed data can be passed to thehost for processing.

In a depth only camera, the sensor and light source will be synchronizedin time. In RGB and depth cameras, the light source and the two sensorswill be synchronized in time, such that both sensors start their framescycles with a known and locked timing relationship, e.g. at the sametime, with each other and the light source. Also, the frame start timeof each sensor can be adjusted with respect to the data stream to thehost to provide a system-level synchronization capability. Data fromeach sensor and audio can be transmitted to host devices on separatestreams over various interfaces, such as a USB2.0 isochronous link,which may include a tagging capability to insert timestamps into eachframe of each sensor. Similarly, the data streams could be integratedbefore transmission and de-integrated by the host.

The camera enables developers to create many new kinds of applications,e.g. gesture control of host devices, interactive games, etc., requiringboth depth and color video.

In a typical Time of Flight (ToF) based camera, the camera is designedto synchronously modulate a light source at a fixed Peak Optical Power(POP) level with a sensor's active integration period, i.e. frame time.In some implementations, camera operating frequencies are varied infairly narrow ranges, e.g. +/−20 MHz, to be able to detect distancealiasing artifacts caused by frequency wrap around or reflections ofobjects beyond the camera's working range created by frequency rangemultiples. In ToF based cameras, frequency is proportional to distance,e.g. an object at 6 m, which is lm outside a 5 m range of interest, canbe falsely detected as an object of low reflectivity at 3 m, a distancewithin the range of interest.

An object of the present invention is to overcome the shortcomings ofthe prior art by providing a depth camera for a ToF system that dividesthe overall range of interest and Field of View (FoV) into Volume ofInterest (VOI) sub-ranges with different frequency , peak optical powerand integration period pairs or triplets for each VOI sub-range.

SUMMARY OF THE INVENTION

Accordingly, the present invention relates to a depth camera for a timeof flight device for presenting three dimensional data to a hostcomprising:

a light source for launching a beam of light at a range of interest fora field of view, the light source having an adjustable frequency and anadjustable peak optical power;

a detector array for receiving and detecting portions of the beam oflight reflected off of objects within the range of interest and field ofview; and

a controller for adjusting the light source frequency and peak opticalpower within a single frame time period in accordance with a pluralityof frequency and peak optical power pairs to obtain a plurality of threedimensional data measurements for each frame,

whereby the range of interest and field of view is divided into aplurality of volumes of interest, each volume of interest having adifferent, frequency, peak optical power, and minimum and maximumdistance from the light source, to increase dynamic range and depth offield within each volume of interest.

Another aspect of the present invention relates to a method of operatinga depth camera comprising:

a) launching light from a light source at a range of interest over afield of view; and

b) receiving and detecting portions of the beam of light reflected offof various objects within the range of interest and the field of view;

wherein step a) includes:

launching a first beam of light at a first frequency and a first peakoptical power for a first integration period within a single frame timeperiod to increase depth of field and dynamic range within a firstvolume of interest to generate a first three dimensional datameasurement;

launching a second beam of light at a second frequency greater than thefirst frequency and a second peak optical power less than the first peakoptical power for a second integration period within the same singleframe time period to increase depth of field and dynamic range within asecond volume of interest to generate a second three dimensional datameasurement; and

launching a third beam of light at a third frequency greater than thesecond frequency and a third peak optical power less than the secondpeak optical power for a third integration period within the same singleframe time period to increase depth of field and dynamic range within athird volume of interest to generate a third three dimensional datameasurement.

Yet another aspect of the present invention includes a time of flightbased depth camera for presenting three dimensional data to a hostdevice comprising:

a light source for launching a beam of light at a range of interest fora field of view, the light source having variable integration timeperiods and peak optical power;

a detector array for receiving and detecting portions of the beam oflight reflected off of objects within the range of interest and field ofview; and

a controller for adjusting the light source integration time period andpeak optical power within a single frame time period in accordance witha plurality of integration time period and peak optical power pairs toobtain a plurality of three dimensional data measurements,

whereby the range of interest and field of view is divided into aplurality of volumes of interest, each volume of interest having adifferent, integration time period, peak optical power, and minimum andmaximum distance from the light source, to increase dynamic range anddepth of field within each volume of interest.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in greater detail with reference to theaccompanying drawings which represent preferred embodiments thereof,wherein:

FIG. 1 is an isometric view of a depth camera in accordance with thepresent invention;

FIG. 2 is a schematic representation of the depth camera of FIG. 1 withpredefined volume of interest sub-ranges in accordance with the presentinvention;

FIG. 3 is a plot of volume of interest sub-range triplet information inaccordance with the present invention; and

FIG. 4 is a schematic representation of and an ASIC of the depth cameraof the present invention.

DETAILED DESCRIPTION

With reference to FIG. 1, a depth camera 1, in accordance with thepresent invention, for a Time of Flight (ToF) system, e.g. for a gesturerecognition device, includes a light source 2, e.g. an LED, Laser orother light emitting device with associated drive and control circuitry,for launching a beam of light into an overall Range of Interest (RoI)and Field of View (FoV), a receiving optic with an IR filter, and adepth sensor detector array 3 for receiving and detecting portions ofthe beam of light reflected off of various moving objects within the RoIand FoV. The depth camera 1 also includes a power port 4 for connectionto a remote or host power supply, and a data port 6 for connection to ahost processor. In the illustrated application, a color (RGB) camera 7is also provided, along with variable speed fans 8 for cooling thesystem.

When considering dynamic range and depth of field, higher frequenciesand lower powers work well for short range applications (0.5 mm to 3 m),low frequencies and high powers work well for long range applications (3m to 5 m), and something in between is better for intermediate rangeapplications (2 m to 4 m). However, the camera 1, of the presentinvention, provides a working range of between 0.5 mm and 5 m or more.

With reference to FIG. 2, the RoI and FoV, for the camera 1 according tothe present invention, is divided into a plurality of sub-range volumesof interest (VoI), 16, 17 and 18, each with their own operatingfrequency and synchronized with a different light source peak opticalpower (POP) during a integration subperiod within the camera's frametime to create frequency, POP and integration subperiod pairs ortriplets more finely tuned for the plurality of sub-ranges within thecamera application's range of interest. The summing or aggregation ofthese sub-range intra-frame time frequency, POP and integrationsubperiod pairs or triplets creates a higher dynamic range and sharperdepth of field image within the given overall Rot Three VoI's areillustrated; however, two, four or more VoI's are possible and withinthe scope of this invention.

An aggregation process is used to stitch together intra frame depthimage fragments generated by the depth camera 1 using optical power,frequency and integration period pairs or triplets into a single ormultiple frame composite image(s). Such aggregation could be done by,but not limited to, the simple or weighted averaging of individual pixelvalues generated by intra frame or multiple frame pairs, triplets,quadruplets, etc. Similarly mean values, mode values, etc. could beused.

The determination of appropriate frequency, power values and ideallyintegration subperiods can be made via estimation, calculation orempirically for static or dynamic scenes, statically, e.g. during aninitial set up, or dynamically, e.g. during use. An example of a simplestatic estimation would be to break the FOV Volume Of Interest (VOI)into a plurality of sections, e.g. two to five or more VoI sub-ranges,in the depth direction and assume that the power required for successivesections would increase moving away from the camera. The appropriatenumber of VoI sub-ranges is dependent on the application's overall rangeand depth of field requirements, and typical object reflectivity's inthe range, i.e. longer distances and greater target object reflectivityranges could mean more sections. The VoI sub-ranges can have equalranges, and volumes, e.g. 1.5 m to 3 m, preferably 2 m deep, or they canhave different ranges and volumes, e.g. the first volume 16 is smallerthan the second volume 17, which is smaller than the third volume 18.Typically these sub-ranges or volumes will grow with distance from thecamera 1.

The VoI sub-ranges can be discreet volumes, e.g. VoI 16 has an R¹ _(min)to R¹ _(max) of from 0.5 m to 1.5 m, VoI 17 has a R² _(min) to R² _(max)of from 1.5 m to 3 m, and VoI 18 has a R³ _(min) to R³ _(max) of fromand 3 m to 5 m. Alternatively, the VoI sub-ranges can be a series ofoverlapping volumes, e.g. VoI 16 has an R¹ _(min) to R¹ _(max) of from0.5 m to 2 m, VoI 17 has a R² _(min) to R² _(max) of from 1 m to 3 m,and VoI 18 has a R³ _(min) to R³ _(max) of from and 2 m to 5 m.

Next, with reference to FIG. 3, a frequency f_(n) is selected, e.g. asuitable unambiguous, frequency or the highest (non-aliasing) primefrequency the camera 1 is capable of, within a selected low range offrequencies (10 to 40 MHz) for the farthest VoI sub-range, e.g. VoI 18.

For example: at 5 m R³max, the non-aliasing max frequency is 20 MHz, but19 MHz, which is the highest prime frequency close to but not higherthan 20 MHz, may be the better choice for the farthest VoI subrange 18,so that erroneous readings do not occur due to the closer subranges inwhich the frequency might be set to 40 MHz or 60 MHz, thereby creatinginterfering harmonics. Accordingly, 37 MHz or 59 MHz would likely bebetter choices for the middle subrange VoI 17, and 97 MHz, etc. for thenearest subrange VoI 16. Ideally, the least common multiple of the threefrequencies f₁, f₂, f_(n), selected are outside the working range of thecamera.

The POP P_(n) for the farthest VoI sub-range, e.g. VoI 18, is thendetermined based on the frequency f_(n) and the POP necessary to resolvethe required minimum object size at its lowest targeted reflectivity. Asthe range VoI moves closer to the camera, the frequency and POP valuesare modified to optimize performance within the closer VoI sub-ranges,e.g. VoI sub-ranges 16 and 17, e.g. lower power, higher frequency insuccessive ranges getting closer to camera. The frequency values betweenthe VoI's 16 to 18 are at much wider ranges, e.g. greater than +/−30MHz, 50 MHz and up at least 100 MHz, than prior art systems.

For example: for the farthest VoI sub-range 18 the frequency f_(n)selected might be 10 to 40 MHz, preferably 20 to 25 MHz to avoiddistance aliasing in the range, and the POP P_(n) might be determined tobe 5 W or more, preferably 1 W or more, most preferably greater than 500mW, but ideally as low as possible to reduce power requirements. Themiddle VoI sub-range 17 can have a frequency f₂ higher than the farthestVoI sub-range 18, e.g. 30 to 70 MHz, preferably 40 to 50 MHz to avoiddistance aliasing within this midrange, with a POP P₂ less than thefarthest VoI sub-range 18, e.g. less than half of the farthest sub-rangeor 250 mW to 4 W, preferably 250 mW to 1 W, and most preferably 250 mWto 500 mW, but ideally as low as possible. The closest VoI sub-range 16can have a frequency f₁ higher than the other two or more VoIsub-ranges, e.g. 60 MHz or more, preferably 75 MHz or more, buttypically as high as possible below the distance aliasing frequency,with a POP P₁ less than the other ranges, e.g. 400 mW or less,preferably less than 250 mW, and most preferably 50 mW or less, butideally as low as possible.

In a simple embodiment, the intra-frame integration period I is dividedequally amongst the VoI sub-ranges; however, the intra-frame integrationperiods I₁, I₂, . . . I_(n) can be divided unevenly amongst thefrequency/POP pairs to more optimally allocate power within ordistribute power to the various VoI sub-ranges. Intra-frame integrationtime, frequency and or power might be reduced to avoid saturation ofmore reflective objects with in the range's VOI. For example: anintegration period between say 5% and 40%, preferably between 25% and40%, of the total frame period would be suitable time periods, dependingon system requirement. Typically, the larger VoI sub-ranges and thosewith longer ranges require more time, e.g. a larger percentage of theintegration period.

If it is determined that the frequency, POP and integration subperiodpairs or triplets require less than a full frame period to achievedesired image quality, the light source can be turned off to conservepower and reduce the generation of unwanted heat in the system, asillustrated in FIG. 3.

The aggregation of object depth values across these more optimizedsub-range intra-frame time frequency, POP and integration time tripletsR₁, R₂, . . . R_(n) enables the creation of a higher dynamic range ,sharper depth of field and more accurate depth image of a given range ofinterest. As the VoI sub-ranges move closer to the camera 1, the pair ortriplet values can be modified to optimize performance within the secondsub-range's VoI, e.g. lower power, higher frequency in successive rangesgetting closer to camera.

In a more complex case, e.g. a dynamic scene where objects of varyingbrightness are moving within the scene and various VoI sub-ranges,historical frame data can be used to make predictive modificationsdynamically during camera operation. The object motion is tracked inthree dimensions as well as its brightness. As an example, if in a fewframes of data a bright or highly reflective object is found within aVoI sub-range's moving closer to the camera 1, the triplet R of thatsub-range VoI or zone could be modified, as necessary. For example: thelight source power P could be reduced and/or the frequency f could beincreased and/or the integration period I could be reduced, or anysimilar weighted combinations of these variables could be changed, usingthe components and processes described in the below explanation of the3D camera block diagram, to avoid a saturation issue. Similarly, adarker or less reflective object moving away from the camera 1 couldtrigger modification to a range's VoI triplet to keep the object fromdisappearing while still in the range.

In yet another embodiment, the intra-frame triplet variations could beused in conjunction with an autofocus/zoom lens 9, with or without anequivalent light source zoom capability. In the case of theautofocus/zoom lens 9, a sub-range VoI triplet could become aquadruplet. In addition to modifying one or more of intra-framefrequency, integration time, and optical power, the FOV/VOI could beincreased or decreased as an application required by the widening ornarrowing the FOV/VOI of one of the sub-range VoI's 16 to 18. As anexample, the sub-range VoI's closer to the camera 1 typically requirelarger FOVs than sub-range VoI's further from the camera 1. Narrowing orwidening the camera's FOV has nearly the same effect as increasing ordecreasing POP for a sub-range VoI, the amount of which depends onwhether or not the light source is synchronously zoomed with the lens 9to cover the same FOV. As objects get closer to the camera 1, they getlarger, taller and wider and would benefit from a larger FOV. So, ratherthan simply reducing the POP, frequency or integration period to avoidsaturation, the lens and the light source can be zoomed out, which wouldeffectively reduce the per pixel POP and similarly avoid potentialobject saturation issues. Alternatively, as objects move further fromthe camera 1, they get smaller, shorter and narrower which leaves roomto reduce the cameras FOV. So, rather than simply increasing the POP,frequency or integration period to avoid object disappearance, the lens9 and light source 2 can be zoomed in to effectively increase per pixelPOP. This could significantly reduce the maximum POP and electricalpower requirement of the camera 1 throughout its total range.

In yet another embodiment, the intra-frame triplet, or intra-frametriplet plus zoom lens 9 intra-frame quadruplet variations. could beused in conjunction with lens 9 with variable aperture capability, withor without an equivalent lens or light source zoom capability. In thecase of the variable aperture lens 9, a sub-range VoI triplet couldbecome a quadruplet or quintuplet if used with the lens' zoomcapability. In addition to modifying one or more of intra-framefrequency, integration subperiod, and optical power, the FOV/VOI couldbe increased or decreased as an application required by the widening ornarrowing the lens aperture setting of one of the sub-range VoI's 16 to18. As an example, a camera sub-range VoI may require more or less lightthan the previous or next camera sub-range VoI. Narrowing or wideningthe camera's aperture has nearly the same effect as increasing ordecreasing POP for a sub-range VoI, the amount of which depends onwhether or not the light source 2 is synchronously zoomed and or focusedwith the lens 9 to cover the same FOV.

The light source 2 comprises a laser required to actively illuminate thespecified optical field of view within the camera working range withmodulated light. The light source 2 provides the specified wavelength ofmonochromatic light for the active illumination. A typical light source2 comprises a laser, high speed driver circuitry 10 and a diffuser foruniform light distribution within the FOV. The laser driver circuit 10is controlled with signals coming from a coprocessor 21. The lightsource 2 is modulated during the integration time of the sensor 3 and istightly coupled with sensor operation. Care needs to be taken to controlthe timing and waveform of signals going to the light source 2 andwithin the light source 2 to produce proper illumination over theoperating temperature.

Light source frequency is a critical system performance variable andmust be selected carefully based on camera operating range with higherfrequencies being better for near range applications and lowerfrequencies being better for long range applications. Along withmulti-frequency implementation, aliasing artifacts can be reduced byproper frequency selection for an application.

Depending on sensor architecture and output, the coprocessor 21 isprovided that can translate phase data to depth data, performs depthcalibration, depth data corrections, RGB color processing, compressionsensor control, RGB & Z data synchronization, tagging and registration.For low functioning sensors (RGB or Z), some or all of these aboveprocesses could be handled by the camera coprocessor 21 or raw datacould be passed through to the host for processing. For higherfunctioning sensors, fewer of these processes will need to be handled bythe coprocessor 21 within the camera 1. The choice of coprocessor 21 isvery much dependent on the target host processing capability. Lessintelligent host devices require more in camera processing while moreintelligent host devices can be less dependent on in camera processing.

With reference to FIG. 4, in the present invention, the abovecoprocessor 21 and the following 3D imaging related functions could beimplemented in gate level logic and integrated into a single applicationspecific integrated circuit ASIC 21 or implemented in host side softwareor hardware or any combination in between. In a conventional time offlight based 3D input device, phase data coming from a depth sensor, rawRGB data coming from a traditional color sensor, and audio coming from amicrophone or microphone array must be further processed prior topresentation to various host devices, such as PCs, TVs, mobile devices,etc. for display.

Conventional discrete component implementations require analog todigital converters (ADC) for each of the sensors and microphones, animage correction logic, compression logic and compression memory. Mostof these resources can be shared when consolidated into the ASIC 21resulting in a significant size and cost savings. Similarly, pure logicdevices are typically fabricated on smaller fabrication processgeometries resulting in additional size and cost reductions when the RGBISP, RGB & Z corrections and control functions are moved off sensor intothe ASIC 21.

Depending on the RGB and Depth sensor formats, the raw data streams canexceed the bandwidth of the host input port, typically USB 2.0 and musttherefore be processed and or compressed prior to transport.

The below described functions of the ASIC 21 can be performed fasterwhen implemented in hardware logic as opposed to software running on ahost's processor. If the host's processor is required to perform thebelow mentioned ASIC functions as well as application processing theresult can be increased application latency, which can be distracting toa user. Similarly, keeping data flow on chip during processing canincrease processing speed and further decrease application latency.

An embedded microprocessor/controller 22 controls the flow of data andcommand instructions within the ASIC 21, and turns on or off specificASIC logic block level functions or functions within ASIC logic blocks.The microprocessor 22 also controls data and command instruction flow ofsensors, i.e. the depth sensor 3 and RGB sensor 7, and the light source2, in particular from the sensor and light source control module 23. Themicroprocessor 22 also supports device level user interfacing, e.g.buttons, switches, display 26, etc., and supports firmware basedprocessing functions and programmability, e.g. exposure control, gaincontrol, light source frequency and duty cycle control, depth sensor 3to RGB 7 and light source 2 synchronization, etc.

I2C 27 is a command/instruction bus allowing command and response flowwithin the ASIC 21. I2C 27 is the command, control and feedbackmechanism; however, other standard communication, control and feedbackstandards or proprietary methods could be used. Any 3D processor blockcould be integrated into a single chip or parts in any combination ofdiscrete chips. The system power supply (not shown) could be astandalone power supply, integrated into the 3D processor or receivedfrom a host 28 via an integrated power and data bus such as USB,Firewire, etc.

Analog to digital converter (ADC) 29 converts analog data to digitaldata for further on chip and host processing.

One or more Input/Output Port(s) 31 supports the input of raw orpreprocessed data from the RGB sensor 7, the depth sensor 3, an optionalmicrophone 32, the light source 2 or other data; as well as command,clock or other general purpose input to the ASIC 21 from its peripheralsand from the ASIC 21 to its peripherals. The input/output port 31 alsoprovides processed data output to the display 26.

Flash Memory 33 stores or buffers data from the various input devices,e.g. depth and RGB sensors 3 and 7, for the various on chip processingmodules, e.g. depth processing module 34 and color processing module 36.

RAM 37 stores command and control instruction firmware for execution bythe microprocessor/controller 22.

A Clock/PLL 38 provides an internal or externally synchronized clockreference for chip function timing and control.

The USB Phy 6, which could be PCI, MIPI or any other standard orproprietary Phy provides a physical interface from the ASIC 21 to thehost device 28.

An Audio Codec 41 converts raw or preprocessed audio data from mics 32to an industry standard or proprietary data format for use by the host28.

The Color Processing module 36 performs white balancing/colorcorrection, color demosaicing, color space conversion, and other raw orpreprocessed RGB data stream related processing functions to the datafrom the RGB sensor 7.

The Depth Processing module 34 performs phase to depth data conversion,etc. on raw or preprocessed depth data form the depth sensor 3.

A Corrections module 42 performs lens, Gama, dark level compensation,sensor defect, scaling, horizontal/vertical flip/rotation, filtering,flicker, dealiasing, binning etc.

A Compression module 43 compresses raw or preprocess RGB, Depth, Audioor other data from the corresponding modules 7, 3, 32 to industrystandard, e.g. JPEG, MJPEG, H.264, Dolby AC3, etc. or proprietaryformats for use by host device 28.

A Data Bus 44 transfers data between the functional blocks, e.g. modules3, 7, 32, memory 33, 37 and ports 31 of the ASIC 21 under direction ofthe microprocessor/controller 22.

Synchronization, Tagging & Merging module 44 tags, synchronizes andmultiplexes packetized RGB, Depth and Audio raw or processed datastreams from the corresponding sensors 7, 3 and 32 for transfer andpresentation to the host 28 via the USB Phy 6.

Calibration and Registration module 46 uses algorithms and internalcoefficients created from camera measurements made during thecalibration phase of camera testing to correlate camera depth valueswith actual object distance values. Registration is the process ofcorrelating the x & y locations of pixels between the RGB and Depthsensors.

The microprocessor 22 first applies settings for one of thepredetermined frequency, power and integration period triplet stored inthe RAM 37 or other suitable non-transitory memory. Preferably, themicroprocessor 22 then assesses the image quality, such as depthaccuracy, and image sharpness, e.g. by determining at least one of: thenumber of blurred pixels, the number of saturated pixels, and the numberof dark pixels, etc., within the field of view and volume of interestsub-range, and comparing the determined number to a predeterminedthreshold value, based on algorithms stored in non-volatile memory orhard coded in the processor or other chip. The micro-processor 22 then,using other algorithms stored in memory or hard coded in the processoror other chip, calculates appropriate new triplets and triplet sequencesfor best or improved dynamic range. The micro-processor 22 then adjuststhe clock timing (frequency), light source 2 power level, lens 9 zoomand focus settings corresponding to each sequential triplet, asnecessary. Image quality based feedback loops may or may not be used tovalidate or monitor sensor 3, lens 9 or light source 2 actual settingsor performance. The resulting triplets could be sequenced in any orderand the system could be implemented with a fixed focus lens withappropriate depth of field for the field of view and volume of interest.The micro-processor 22 then merges the data from each triplet into orcalculates a composite frame(s) for transfer to the host device 28.

Such processing and control could also be implemented on and performedby the sensor 3 or the raw data could be transferred to the host 28 forprocessing or in any distributed processing device combination.Similarly, such processing could be performed before, after or duringphase to depth calculation. i.e. on phase, depth/range or intermediatedata; and before, after or during other (calibration, registration,corrections, compression and audio, RGB & Depth data synchronization,tagging and merging, etc.) data processing activities.

We claim:
 1. A depth camera for a time of flight device for presenting three dimensional data to a host comprising: a light source for launching a beam of light at a range of interest for a field of view, the light source having an adjustable frequency and an adjustable peak optical power; a detector array for receiving and detecting portions of the beam of light reflected off of objects within the range of interest and field of view; and a controller for adjusting the light source frequency and peak optical power within a single frame time period in accordance with a plurality of frequency and peak optical power pairs to obtain a plurality of three dimensional data measurements for each frame time period, whereby the range of interest and field of view is divided into a plurality of volumes of interest, each volume of interest having a different, frequency, peak optical power, and minimum and maximum distance from the light source, to increase dynamic range and depth of field within each volume of interest.
 2. The depth camera according to claim 1, wherein initial light source frequency and peak optical power settings for each volume of interest are predetermined and stored in non-volatile memory accessible by the controller.
 3. The depth camera according to claim 2, wherein the controller adjusts at least one of the light source frequency and the peak optical power based on feedback from the detector array.
 4. The depth camera according to claim 1, wherein the controller also adjusts the light source integration period in accordance with predetermined or calculated integration periods for each frequency and peak optical power pair.
 5. The depth camera according to claim 4, further comprising a lens for focusing the beam of light; wherein the controller is also capable of adjusting the focus of the lens along with each frequency, peak optical power and integration period.
 6. The depth camera according to claim 5, further comprising an adjustable aperture for the lens; wherein the controller is also capable of adjusting the adjustable aperture along with each frequency, peak optical power, integration period and lens focus.
 7. The depth camera according to claim 1, further comprising an adjustable lens for focusing the beam of light; wherein the controller is also capable of adjusting the focus of the lens along with each frequency and peak optical power.
 8. The depth camera according to claim 1, further comprising a lens and an adjustable aperture for the lens; wherein the controller is also capable of adjusting the adjustable aperture along with each frequency and peak optical power pair.
 9. The depth camera according to claim 1, wherein the controller is also capable of aggregating the plurality of three dimensional data measurements
 10. The depth camera according to claim 9, further comprising an ASIC incorporating the controller and other control and processing functions of the camera to minimize latency between the depth camera and the host device.
 11. The depth camera according to claim 1, wherein the controller is also capable of dynamically adjusting any one or more of the frequencies, and the peak optical powers depending on a reflectivity of the object.
 12. The depth camera according to claim 1, wherein a first frequency is between 10 and 40 MHz, and a first peak optical power is greater than 1 W.
 13. The depth camera according to claim 1, wherein a second frequency is between 40 and 50 MHz, and a second peak optical power is between 250 mW and 1 W.
 14. The depth camera according to claim 1, wherein a third frequency is greater than 75 MHz, and a third peak optical power is less than 250 mW.
 15. A method of operating a depth camera comprising: a) launching light from a light source at a range of interest over a field of view; and b) receiving and detecting portions of the beam of light reflected off of various objects within the range of interest and the field of view; wherein step a) includes: launching a first beam of light at a first frequency and a first peak optical power for a first integration period within a single frame time period to increase depth of field and dynamic range within a first volume of interest to generate a first three dimensional data measurement, launching a second beam of light at a second frequency greater than the first frequency and a second peak optical power less than the first peak optical power for a second integration period within the same single frame time period to increase depth of field and dynamic range within a second volume of interest to generate a second three dimensional data measurement; and launching a third beam of light at a third frequency greater than the second frequency and a third peak optical power less than the second peak optical power for a third integration period within the same single frame time period to increase depth of field and dynamic range within a third volume of interest to generate a third three dimensional data measurement.
 16. The method according to claim 15, wherein step b) including aggregating the first, second and third three dimensional data measurements.
 17. The method according to claim 15, further comprising adjusting the focus of a lens associated with the light source for each of the first, second and third volumes of interest.
 18. The method according to claim 15, further comprising adjusting an aperture of a lens associated with the light source for each of the first, second and third volumes of interest.
 19. The method according to claim 15, further comprising dynamically adjusting any one or more of the first, second and third frequencies, and the first, second and third peak optical powers depending on a reflectivity of one of the objects.
 20. The method according to claim 15, wherein the first, second and third integration periods are different.
 21. The method according to claim 15, wherein the first frequency is between 20 and 25 MHz, and the first peak optical power is greater than 500 mW.
 22. The method according to claim 15, wherein the second frequency is between 40 and 50 MHz, and the second peak optical power is between 250 and 500 mW.
 23. The method according to claim 15, wherein the third frequency is greater than 60 MHz, and the third peak optical power is less than 250 mW.
 24. A time of flight based depth camera for presenting three dimensional data to a host device comprising: a light source for launching a beam of light at a range of interest for a field of view, the light source having variable integration time periods and peak optical power; a detector array for receiving and detecting portions of the beam of light reflected off of objects within the range of interest and field of view; and a controller for adjusting the light source integration time period and peak optical power within a single frame time period in accordance with a plurality of integration time period and peak optical power pairs to obtain a plurality of three dimensional data measurements, whereby the range of interest and field of view is divided into a plurality of volumes of interest, each volume of interest having a different, integration time period, peak optical power, and minimum and maximum distance from the light source, to increase dynamic range and depth of field within each volume of interest. 